On Tuesday at noon I sat down in a small, semi-soundproofed videoconference room to attend a couple meetings remotely; a normal, daily event at work. At 12:52pm my phone rang from a phone number I didn't recognize. I silenced it. Then someone on a work group chat said they were leaving campus for the evacuation. I typed back asking what evacuation?

As I was trying to pay attention to the meeting while making sense of what I was reading, I heard yelling in the hallway. I cracked the door open and caught something along the lines of "... out of the building! This is NOT a drill!"

I turned back to the meeting. "Sorry everyone, we're being told to evacuate the building. It's not a drill," and hung up. I ran past my desk which was on the way to the exit. Everyone else in my area had left, but I mindlessly grabbed my coat and bag before heading downstairs by the side exit. Sirens and police cars were now screeching around us. People who looked like security personnel waved me towards the parking lot. I asked them what was going on, and they told me that we had an active shooter in the building across the street.

CNN.com photo by Jeff Chiu / AP

I reached the gathering crowd of a few hundred colleagues. I scanned the faces around me, recognizing and nodding at a few, before seeing my team gathered in a cluster. We acknowledged each other as we tried to account for the others. Have you seen...? Have you heard from...? The group chat had people reporting in, telling us where they were, who they were with, and whether they had left the scene.

shooter at youtube. we're evacuated I texted to my wife & family.

The thumping helicopters above us was a reminder that this was publicly unfolding, and we were still in the middle of it. At this point we still didn't really know exactly what was going on. Active shooter? One or more? Was the situation still active? Were we still in danger or were we safe? More people were walking or driving away as more police showed up, enveloping us.

Omg careful!

yes accounting for everyone

When we weren't scanning the area, we were on our phones. We were all trying to find out more information as others were pinging us on chat and SMS. The news had gotten out.

You OK? Paolo are you ok? Please tell me you are ok. Hey man you ok? You okay? Just saw the report about a shooter at YouTube. i hope you're ok bro. Hey man hoping you're ok. Just heard about the crazy shit in San Bruno. Are you ok?

evacuated. trying to find out latest. team is accounted for

Post an update to say you are ok. Sure many are worried

There were people barricaded inside conference rooms in the other two buildings directly across the street from us. Some had evacuated in a rush and left their phones and laptops; unable to contact anyone, they borrowed others' phones to let their families know they were okay. One of the YouTube executives with us would stand on top of a car in the parking lot to share what little information and instruction we had.

Can you come home?

in a bit yes

Speculation was rampant. It was a woman shooter. People were specifically being targeted. It was an Asian woman. It was a love triangle gone wrong. Two people were shot. There was a hostage situation. There was an accomplice on the loose. Three people were taken to one hospital, four to another. Information was traded in hushed, conspiratorial tones. None of it made sense even as we tried to make sense of the chaos.

I put my bag in my car and wore my jacket. I grabbed the external battery for my phone - I didn't know how much longer this was going to be, and I didn't want my phone to run out. We had accounted for everyone on our team and let others know we were safe. At this point almost my entire team had left the immediate area. Many had gone home. Some had gathered in a building farther away, their wallet, keys, and other personal items stuck on their desks.

The police, wearing bulletproof vests and badges, came over to us. If you saw or heard anything, please come talk to us over there pointing to a spot behind them. If you didn't, stay back there pointing to the back half of the parking lot where we had gathered. A few people moved forward.

They started yelling at someone who had come out of our building. Rifles pointed, they marched towards him. Hands up! Don't move! We watched as they patted him down, pulled his arms behind his back, and checked him out. After a minute or so they let him go to join the rest of us. Then a minute later two of them came back through the crowd to scrutinize his identification before walking away again.

Quite a few people were watching live news on their phones, some with footage taken from the hospitals hovering overhead. The police moved close to us. A suspect is at large so it's better to stay here where it's safe. They were now actively preventing people from leaving the area and telling people to get out of their cars.

a suspect is at large

Omg really? Stay close to a car

can't go anywhere

A crisis counselor from the city of San Bruno inquired how we were doing, moving from cluster to cluster. How are you guys doing? How are you feeling? There were a couple parked buses in the parking lot. They told people to use those bathrooms since we weren't allowed to go into the building. Some had to relieve themselves behind some trees.

The news had been reporting that the incident was over and that the shooter had been found dead at the scene from a self-inflicted gunshot wound, and that three people had been taken to nearby hospitals.

Another half hour later, they cleared our building. We were escorted back in to use the bathrooms but not back to our desks. They corralled us into the large conference room and brought in snacks and drinks. The police took our names and contact information. I ate a banana.

When I was finally cleared by the police, I walked to my car, responded to a couple more messages, and drove home. It had been about three hours.